Metal belt for continuously variable transmission

ABSTRACT

In a metal belt for a continuously variable transmission having a saddle face of a metal element and a rocking edge positioned at substantially the same position in the radial direction, a rocking edge is provided at a radially outer end of a front face of a body part, the rocking edge being a fulcrum for pitching of the metal element of the metal belt which is wound around a drive pulley and a driven pulley and transmits a driving force between the two pulleys, and a recess is provided extending from a front face of a neck part to a front face of the body part. Thus, it is possible to minimize a space created between the front and rear metal elements and reduce the bending stress applied to the metal elements, thereby minimizing degradation of the power transmission efficiency.

TECHNICAL FIELD

The present invention relates to a metal belt for a continuouslyvariable transmission, the metal belt, which is wound around a drivepulley and a driven pulley and transmits a driving force between the twopulleys, including a pair of metal ring assemblies that are arrangedside by side in a left-and-right direction and a large number of metalelements that are latched to the pair of metal ring assemblies in astate in which the metal elements are stacked in a fore-and-aftdirection.

BACKGROUND ART

An arrangement in which a V-shaped block (metal element) is formed so asto have rocking edges in two steps at different levels in the heightdirection of the V-shaped block, and the lower step rocking edge amongthese rocking edges and a band-wound face (saddle face) within aband-assembly groove (ring slot) against which an inner peripheral faceof an endless band (metal ring assembly) abuts are positioned at thesame level in the height direction of the V-shaped block is known fromPatent Document 1 below.

Due to this arrangement it becomes possible to prevent frictional lossby maintaining constant relative positions, in the direction of travel,on the band-wound face of adjacent V-shaped blocks between apulley-wound region and a linear region of the endless band, and it alsobecomes possible, even when the pulley-winding diameter of the endlessband changes from a large diameter to a medium diameter and to a smalldiameter, to accordingly change the relative inclined positions ofadjacent V-shaped blocks owing to the rocking edges formed in two stepshaving different levels, thereby suppressing the amount of coredisplacement of the endless band between pulleys accompanying a changein speed.

Furthermore, a transmission belt (metal belt) in which a rocking edge,which is the center of rotation of adjacent elements that abut againsteach other, is formed at a position separated further toward the innerperipheral side than a saddle face of the element, at least one slitpart housing a sub ring binding a plurality of elements arranged in anannular manner being formed further radially inside than the saddle facein the radial direction of the ring is known from Patent Document 2below.

In accordance with this arrangement, since the elements can be bound notonly by layered rings (metal ring assembly) layered on the saddle facebut also by the sub ring inserted into the slit part, the total numberof rings for binding the elements can be increased by at least one, andbecause of this the durability and the torque capacity of thetransmission belt can be improved. Furthermore, since the sub ringinserted into the slit part is disposed at a position closer to therocking edge than the other layered rings are, the friction between thesub ring and the slit part is small, and it is possible to prevent orsuppress friction due to the number of rings being increased, anyaccompanying power loss, and degradation of the power transmissionefficiency.

Moreover, an arrangement in which a rocking edge and a saddle face of anelement are made to coincide, and when shaping the element by pressforming such as punching out, the rocking edge is provided on a face onthe side where a sharp edge can be formed is known from Patent Document3 below.

In accordance with this arrangement, since the rocking edge of theelement can be formed on the sharp edge, which is not influenced by‘rollover’ when carrying out press forming, for example, it becomespossible to form the rocking edge and a face that the inner peripheralface of a ring abuts against when the ring is wound around the elementat substantially the same position in the height direction of theelement. As a result, relative slippage between the rocking edge and theinner peripheral face of the ring can be reduced, and frictional lossdue to relative slippage can be decreased, thus improving thetransmission efficiency of the transmission belt (metal belt).

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Patent No. 3695216

Patent Document 2: International Patent Application Laid-open No.WO2012/131841

Patent Document 3: Japanese Patent No. 4424376

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, in the arrangement disclosed in Patent Document 1 above, sincethe endless band is disposed in a middle part of the V-shaped block, theheight of a pulley abutment face of the V-shaped block that abutsagainst the V-face of the pulley becomes high, and not only is there theproblem that the distance that the V-shaped block can move in the radialdirection is restricted and the ratio range becomes small, but there isalso the problem that since the rocking edges are formed with two steps,production of the V-shaped block becomes cumbersome, and the costincreases.

Furthermore, paragraph [0011] of Patent Document 1 above states that ‘ifthe rocking edge were to be provided on a border part between a basepart and a band-assembly groove of the V-shaped block, since theposition of this border part would also correspond to a border partbetween a base part and a band-assembly groove of an adjoining V-shapedblock, the rocking edge would drop into the band-assembly groove of anadjoining V-shaped block, the V-shaped blocks would be displacedrelative to each other in the height direction, and this could not be afundamental solution’, but this suggests on the contrary that theproblems could be solved if the structure were such that there would beno problem if the rocking edge dropped into the band-assembly groove ofan adjoining V-shaped block.

Moreover, the arrangement disclosed in Patent Document 2 above has theproblem that even if the sub ring inserted into the slit part isdisposed at a position close to the rocking edge, since the otherlayered rings are disposed at positions further away from the rockingedge, it cannot prevent a frictional force from occurring between thesaddle face and the layered rings.

Furthermore, in the arrangement disclosed in Patent Document 3 above, asdescribed for the problem in Patent Document 1 above, there is apossibility that the rocking edge will drop into the band-assemblygroove of an adjoining element, and the element will be displaced in theheight direction. Moreover, since first elements and second elementsthat have different shapes are stacked in turn, there is the problemthat management of the order of stacking thereof becomes troublesome,and the ease of assembly is degraded.

The present invention has been accomplished in light of the abovecircumstances, and it is an object thereof to provide a metal belt for acontinuously variable transmission in which a saddle face and a rockingedge of a metal element are formed at substantially the same position inthe radial direction, degradation of the efficiency of transmitting thedriving force being minimized by enabling displacement of the metalelement in the radial direction and in the rotational direction to beallowed.

Means for Solving the Problems

In order to attain the above object, according to a first aspect of thepresent invention, there is provided a metal belt for a continuouslyvariable transmission, the metal belt, which is wound around a drivepulley and a driven pulley and transmits a driving force between the twopulleys, comprising a pair of metal ring assemblies that are arrangedside by side in a left-and-right direction and a large number of metalelements that are latched to the pair of metal ring assemblies in astate in which the metal elements are stacked in a fore-and-aftdirection, the metal element comprising a pair of ring slots with whichthe pair of metal ring assemblies engage, a neck part that is positionedbetween the pair of ring slots, a body part on which is formed a saddleface that is continuous with a radially inner side of the neck part andsupports an inner peripheral face of the pair of metal ring assemblies,and an ear part that is continuous with a radially outer side of theneck part and opposes an outer peripheral face of the pair of metal ringassemblies, and a rocking edge being provided at a radially outer end ofa front face of the body part, the rocking edge being a fulcrum forpitching of the metal element, wherein a first recess extending from theneck part to the body part is formed in front faces of the neck part andthe body part.

Further, according to a second aspect of the present invention, inaddition to the first aspect, a second recess extending from the neckpart to the body part is formed in rear faces of the neck part and thebody part.

Furthermore, according to a third aspect of the present invention, inaddition to the first aspect, the first recess is formed so as to extendfrom one part of the neck part to the body part, a third recessextending from one part of the neck part to the ear part is formed inrear faces of the neck part and the body part, and the first recess andthe third recess are positioned so as not to overlap one another whenviewed in the fore-and-aft direction.

Effects of the Invention

In accordance with the first aspect of the present invention, the metalelement of the metal belt, which is wound around the drive pulley andthe driven pulley and transmits a driving force between the two pulleys,includes the pair of ring slots, the neck part, the body part, and theear part. Since the rocking edge, which becomes a fulcrum for the metalelement to undergo pitching, is provided on the radially outer end (thefront end of the saddle face) of the front face of the body part, evenwhen the metal element undergoes pitching, it is possible to preventslippage from occurring between the saddle face of the body part of themetal element and the inner peripheral face of the metal ring assembly,and the power transmission efficiency of the metal belt can be enhanced.

Since the first recess extending from the neck part to the body part isformed in the front faces of the neck part and the body part, when themetal element on the rear side is displaced toward the radially outerside with respect to the metal element on the front side, the rockingedge of the metal element on the rear side enters the ring slot of themetal element on the front side, and the metal element on the rear sidemoves so as to be closer to the metal element on the front side, therebyenabling the inclined face of the body part of the metal element on therear side to abut against the body part of the metal element on thefront side via the entire length in the left-and-right direction. As aresult, the bending load applied to the portion where the neck part isconnected to the body part decreases, and bending of the neck part issuppressed, thus minimizing degradation of the power transmissionefficiency.

When the metal elements on the front side and the rear side rotaterelative to each other around the axis in the fore-and-aft direction,since a space is created between the rear face (the rear end of thesaddle face) of the body part of the metal element on the front side andthe front face (inclined face) of the body part of the metal element onthe rear side, the body part undergoes bending deformation so as toclose the space by means of the pushing force between the metalelements, thus causing degradation of the strength and degradation ofthe power transmission efficiency. However, since the first recess ofthe metal element extends from the neck part to the body part, thestarting point of the space moves due to the first recess and the lengthin the left-and-right direction of the space is extended, therebyreducing the bending stress (or the amount of relative deformation) ofthe body part required in order to close the space and minimizingdegradation of the strength and degradation of the power transmissionefficiency.

Furthermore, in accordance with the second aspect of the presentinvention, since the second recess extending from the neck part to thebody part is formed in the rear faces of the neck part and the bodypart, due to the second recess functioning in the same manner as thefirst recess, even if the front and rear metal elements are displaced inthe radial direction or in the rotational direction, it is possible tominimize degradation of the power transmission efficiency.

Moreover, in accordance with the third aspect of the present invention,since the first recess is formed so as to extend from one part of theneck part to the body part, the third recess extending from one part ofthe neck part to the ear part is formed in the rear faces of the neckpart and the body part, and the first recess and the third recess arepositioned so as not to overlap one another when viewed in thefore-and-aft direction, due to the first recess, even if the metalelement on the front side and the metal element on the rear side aredisplaced in the radial direction or in the rotational direction, notonly is it possible to minimize degradation of the power transmissionefficiency, but it is also possible to efficiently transmit the drivingforce by stabilizing the attitude of the metal element by making therear face of the neck part of the metal element on the front side(portion where the third recess is not formed) abut against the frontface of the neck part of the metal element on the rear side (portionwhere the first recess is not formed).

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] FIG. 1 is a perspective view showing part of a metal belt for acontinuously variable transmission. (first embodiment)

[FIG. 2] FIG. 2 is a diagram showing the shape of a metal element.(first embodiment)

[FIG. 3] FIG. 3 is a diagram for explaining the operation when there isdisplacement of the metal element in the radial direction. (firstembodiment)

[FIG. 4] FIG. 4 is a diagram for explaining the operation when there isdisplacement of the metal element in the rotational direction. (firstembodiment)

[FIG. 5] FIG. 5 is a diagram showing the shape of a metal element.(second embodiment)

[FIG. 6] FIG. 6 is a diagram for explaining the operation when there isdisplacement of the metal element in the radial direction. (secondembodiment)

[FIG. 7] FIG. 7 is a diagram for explaining the operation when there isdisplacement of the metal element in the rotational direction. (secondembodiment)

[FIG. 8] FIG. 8 is a diagram showing the shape of a metal element.(third embodiment)

[FIG. 9] FIG. 9 is a diagram for explaining the operation when there isdisplacement of the metal element in the radial direction. (thirdembodiment)

[FIG. 10] FIG. 10 is a diagram showing the shape of a metal element.(Comparative Example)

[FIG. 11] FIG. 11 is a diagram for explaining the operation when thereis displacement of the metal element in the radial direction.(Comparative Example)

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS

-   11 Metal belt-   13 Metal ring assembly-   14 Metal element-   15 Body part-   15 a Saddle face-   15 b Inclined face-   16 Neck part-   17 Ear part-   18 Ring slot-   19 Rocking edge-   20 First recess-   20′ Second recess-   20″ Third recess

MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are explained by reference to theattached drawings.

First Embodiment

First, referring to FIG. 1 to FIG. 4 a first embodiment of the presentinvention is explained.

As shown in FIG. 1, a metal belt 11 that is wound around a drive pulleyand a driven pulley of a belt type continuously variable transmissionand transmits a driving force is formed from a pair of metal ringassemblies 13 and 13 formed by layering a plurality of metal rings 12,and a large number of metal elements 14 supported on the pair of metalring assemblies 13 and 13.

In the present specification, the fore-and-aft direction is defined withthe direction of travel of the metal belt 11 as forward and thedirection opposite thereto as rearward. Furthermore, the radialdirection is defined as a direction perpendicular to the fore-and-aftdirection with the outer peripheral side of a pulley that the metal belt11 is wound around as the outer side and with the center side as theinner side. Moreover, the left-and-right direction is defined as adirection that is perpendicular to the fore-and-aft direction and theradial direction and in which the pair of metal ring assemblies 13 and13 are arranged side by side.

As shown in FIG. 1 and FIG. 2, the metal element 14 is formed bypunching out a metal plate by press forming, and includes asubstantially trapezoidal body part 15 on the radially inner side, aneck part 16 extending from the middle in the left-and-right directionof the body part 15 toward the radially outer side, and a triangular earpart 17 connected to the radially outer side of the neck part 16 andextending toward opposite sides in the left-and-right direction. A pairof ring slots 18 and 18 are formed at positions sandwiched by the outeredge in the radial direction of the body part 15, the outer edge in theleft-and-right direction of the neck part 16, and the inner edge in theradial direction of the ear part 17, the ring slots 18 and 18 opening tothe outside in the left-and-right direction and housing the pair ofmetal ring assemblies 13 and 13.

Saddle faces 15 a and 15 a are formed on radially outer faces of thebody part 15 that face the ring slots 18 and 18, inner peripheral facesof the metal ring assemblies 13 and 13 abutting against the saddle faces15 a and 15 a. An inclined face 15 b is formed on a front face of thebody part 15, the inclined face 15 b tapering so as to decrease inthickness in going from the radially outer side toward the radiallyinner side, and a rocking edge 19 extending linearly in theleft-and-right direction is formed at a position where the radiallyouter end of the inclined face 15 b intersects the front end of thesaddle faces 15 a and 15 a. A pair of pulley abutment faces 15 c and 15c are formed at opposite ends in the left-and-right direction of thebody part 15, the pulley abutment faces 15 c and 15 c being capable ofabutting against a V-face of a pulley.

A first recess 20 is formed in a front face of the metal element 14, thefirst recess 20 extending over the entire region of the neck part 16, amiddle part in the left-and-right direction of the ear part 17, and amiddle part in the left-and-right direction of the body part 15. Thefirst recess 20 is formed by hollowing out part of a front face of themetal element 14, which is basically a flat face, at a constant depth,the corners thereof being a step rising sharply at right angles.However, since the front face of the body part 15 is the inclined face15 b, a radially inner edge 20 a of the first recess 20 is smoothlycontinuous with the inclined face 15 b on the radially inner side of therocking edge 19.

A truncated conical nose 17 a projecting forward is formed on a frontface of the middle of the ear part 17, and a hole 17 b is formed in arear face of the middle of the ear part 17, the hole 17 b openingrearward and the nose 17 a being capable of fitting thereinto. The nose17 a and the hole 17 b fit together with a slight gap therebetween, andthis therefore allows adjacent front and rear metal elements 14 and 14to move in parallel to each other in a range corresponding to the gapand to rotate relative to each other around the axis in the fore-and-aftdirection. A pair of flat portions 17 c and 17 c are formed on oppositeend parts in the left-and-right direction of the ear part 17 so as tosandwich the first recess 20. The height of the flat portions 17 c and17 c is flush with the height of the rear face of the body part 15.

The operation of the first embodiment of the present invention havingthe above arrangement is now explained.

The metal belt 11 wound around the drive pulley and the driven pulleytransmits a driving force by the pushing force of a chord sectionextending linearly from the drive pulley toward the driven pulley. Inthe chord section, the metal elements 14 are aligned in parallel to eachother, whereas in a wound section where the metal belt 11 is woundaround the pulley, since the metal elements 14 change their attitude ina radial manner with the center on the axis of the pulley, they swingrelative to each other so that the gap between the outer ends in theradial direction of the adjacent metal elements 14 increases and the gapbetween the inner ends in the radial direction decreases. In thisprocess, the rocking edge 19 of the metal element 14 on the rear sideabutting against the rear face of the metal element 14 on the front sidebecomes a fulcrum, and the front and rear metal elements 14 and 14undergo pitching (swinging in the fore-and-aft direction) relative toeach other in a range corresponding to the gap between the nose 17 a andthe hole 17 b, thus allowing the attitude to change.

Furthermore, since the metal element 14 of the present embodiment hasthe rocking edge 19 formed at the front ends of the saddle faces 15 aand 15 a, and the height in the radial direction of the rocking edge 19coincides with the height in the radial direction of the saddle faces 15a and 15 a, when the metal elements 14 undergo pitching in the woundsection, the saddle faces 15 a and 15 a of adjacent metal elements 14and 14 are prevented from being separated in the fore-and-aft direction,and degradation of the power transmission efficiency due to slippageoccurring between the saddle faces 15 a and 15 a and the innerperipheral faces of the metal ring assemblies 13 and 13 can be avoided.If the rocking edge 19 were to be provided further radially inward thanthe saddle faces 15 a and 15 a, when the metal elements 14 underwentpitching in the wound section, the saddle faces 15 a and 15 a ofadjacent metal elements 14 and 14 would be separated in the fore-and-aftdirection, and there would therefore not only be the occurrence ofslippage between the saddle faces 15 a and 15 a and the inner peripheralfaces of the metal ring assemblies 13 and 13, but also the powertransmission efficiency would deteriorate due to the metal ringassemblies 13 and 13 being stretched.

With regard to adjacent metal elements 14 and 14, the nose 17 a of themetal element 14 on the rear side is fitted into the hole 17 b of themetal element 14 on the front side, and their positions are restrictedby the tension of the metal ring assemblies 13 and 13 pushing the saddlefaces 15 a and 15 a toward the radially inner side, but since there is agap between the nose 17 a and the hole 17 b, radial displacement of themetal elements 14 in the chord section cannot be avoided.

FIG. 10 shows the shape of a metal element 14 of a Comparative Example,which does not have a first recess 20 in a front face. FIG. 11 shows theoperation when the metal element 14 of the Comparative Example isdisplaced in the radial direction. FIGS. 11 (A) and (B), whichcorrespond to a sectional view along line P-P and a sectional view alongline Q-Q in FIG. 10 respectively, show states in which the metal element14 on the rear side is displaced toward the radially inner side withrespect to the metal element 14 on the front side; in this case theentire length of the rocking edge 19 of the metal element 14 on the rearside abuts against the rear face of the body part 15 of the metalelement 14 on the front side, and transmission of the driving force iscarried out efficiently.

However, as shown in FIGS. 11 (C) and (D), which correspond to thesectional view along line P-P and the sectional view along line Q-Q inFIG. 10 respectively, when the metal element 14 on the rear side isdisplaced toward the radially outer side with respect to the metalelement 14 on the front side, a middle part in the left-and-rightdirection of the rocking edge 19 of the metal element 14 on the rearside can abut against the rear face of the neck part 16 of the metalelement 14 on the front side, opposite end parts in the left-and-rightdirection of the rocking edge 19 of the metal element 14 on the rearside oppose the ring slots 18 and 18 of the metal element 14 on thefront side, and a gap occurs between the rocking edge 19 and the rearface of the metal element 14 on the front side. As a result, only part(the middle part in the left-and-right direction) of the rocking edge 19transmits the driving force, a bending load occurs in a portion wherethe neck part 16 is connected to the body part 15, and there are theproblems that the strength is degraded and the transmission of drivingforce cannot be carried out efficiently.

FIG. 3 shows the operation when the metal element 14 of the presentembodiment is displaced in the radial direction. FIGS. 3 (A) and (B)show a state in which the metal element 14 on the rear side is displacedtoward the radially inner side with respect to the metal element 14 onthe front side, and in this case, although the first recess 20 does notfunction, since the entire length of the rocking edge 19 of the metalelement 14 on the rear side abuts against the rear face of the body part15 of the metal element 14 on the front side in the same manner as inthe Comparative Example of FIGS. 11 (A) and (B), bending of the neckpart 16 does not occur, and the efficiency of transmitting the drivingforce does not deteriorate.

On the other hand, as shown in FIGS. 3 (C) and (D), when the metalelement 14 on the rear side is displaced toward the radially outer sidewith respect to the metal element 14 on the front side, since therocking edge 19 at the lower end of the neck part 16 on the front faceof the metal element 14 on the rear side disappears due to the firstrecess 20 formed therein, while the inclined face 15 b of the body part15 of the metal element 14 on the rear side is in sliding contact withthe rear ends of the saddle faces 15 a and 15 a of the metal element 14on the front side, the metal element 14 on the rear side can moveforward so as to be closer to the metal element 14 on the front sidewhile moving toward the radially outer side.

In this way, due to the metal element 14 on the rear side moving forwardso as to be closer to the metal element 14 on the front side whilemoving toward the radially outer side, abutment between the inclinedfaces 15 b and 15 b of the metal element 14 on the rear side and therear ends of the saddle faces 15 a and 15 a of the metal element 14 onthe front side is maintained, it therefore becomes possible to transmitthe driving force via the entire length in the left-and-right directionof the inclined faces 15 b and 15 b, the bending load applied to aportion where the neck part 16 is connected to the body part 15decreases, and bending of the neck part 16 is suppressed, thusminimizing degradation of the strength and degradation of the efficiencyof transmitting the driving force.

Furthermore, since the flat portions 17 c and 17 c at opposite ends inthe left-and-right direction of the front face of the ear part 17sandwiching the first recess 20 are aligned at the same height as thatof the rocking edge 19, when the metal elements 14 are in the chordsection between the drive pulley and the driven pulley, not only do themetal element 14 on the front side and the metal element 14 on the rearside abut against each other via the rocking edge 19, but the metalelement 14 on the rear side abuts against the rear face of the metalelement 14 on the front side also via the flat portions 17 c and 17 c ofthe ear part 17. As a result, the metal elements 14 that are in thechord section and are not displaced in the radial direction abut againsteach other via both the pair of flat portions 17 c and 17 c of the earpart 17 and the rocking edge 19, and it is thus possible for them tomaintain a stable attitude by being aligned in parallel to each otherwithout undergoing pitching.

In addition, as shown in FIGS. 3 (C) and (D), when the metal element 14on the rear side is displaced toward the radially outer side withrespect to the metal element 14 on the front side and moves forward sothat the rocking edge 19 of the metal element 14 on the rear side entersthe ring slots 18 and 18 of the metal element 14 on the front side,since the flat portions 17 c and 17 c of the ear part 17 of the metalelement 14 on the rear side cannot move forward because of interferencewith the rear face of the ear part 17 of the metal element 14 on thefront side, the radially outer end of the metal element 14 on the rearside attempts to fall rearward. However, since the flat portions 17 cand 17 c of the ear part 17 can easily elastically deform rearward via apart where they are connected to the first recess 20, accompanyingforward movement of the rocking edge 19 of the metal element 14 on therear side, the flat portions 17 c and 17 c of the ear part 17 of themetal element 14 on the rear side undergo rearward elastic deformation,and adjacent front and rear metal elements 14 and 14 can maintain amutually parallel positional relationship.

FIG. 4 (B) corresponds to a metal element 14 of a Comparative Example,which does not have a first recess 20, and shows the state when twoadjacent metal elements 14 and 14 are viewed from the front face side;the metal element 14 on the far side is rotated only by an angle θ inthe clockwise direction around a center of rotation O with respect tothe metal element 14 on the near side. The reason that the pair of metalelements 14 and 14 rotate relative to each other around the center ofrotation O is because each metal element 14 is restricted by two metalring assemblies 13 and 13, and an intermediate position between left andright saddle faces 15 a and 15 a that the two metal ring assemblies 13and 13 abut against becomes the center of rotation O. Adjacent metalelements 14 and 14 engage with each other via a nose 17 a and a hole 17b formed on the ear parts 17 and 17, but since there is predeterminedplay between the nose 17 a and the hole 17 b, relative rotation of thepair of metal elements 14 and 14 around the center of rotation O isallowed.

The lower part of FIG. 4 (B) shows a sectional view that is sectioned bya sectional line along the rocking edge 19 of the metal element 14 onthe near side, and with regard to the metal element 14 on the near side,a neck part 16, which is sectioned by the sectional line, appearsbetween the left and right saddle faces 15 a and 15 a. On the otherhand, with regard to the metal element 14 on the far side, the body part15 on the right-hand side in the figure is not sectioned, and the saddleface 15 a on the right-hand side in the figure is thus shown, but theneck part 16 and the body part 15 on the left-hand side in the figureare sectioned by the sectional line. Since an inclined face 15 b, whichis inclined from the saddle face 15 a toward the radially inner side, isformed on a front face of the body part 15, and the thickness in thefore-and-aft direction of the body part 15 gradually reduces in goingtoward the radially inner side, the thickness of the body part 15sectioned by the sectional line reduces further in going to theleft-hand side in the figure, and due to a gap g being created betweenthe left end of the body part 15 of the metal element 14 on the nearside and the left end of the body part 15 of the metal element 14 on thefar side, a triangular space α with the center of rotation O as astarting point is formed between the rear face of the body part 15 ofthe metal element 14 on the near side and the front face (inclined face15 b) of the body part 15 of the metal element 14 on the far side.

In this way, if the two adjacent metal elements 14 and 14 rotaterelative to each other around the center of rotation O, the space α iscreated between the rear face of the body part 15 of the metal element14 on the near side and the front face (inclined face 15 b) of the bodypart 15 of the metal element 14 on the far side, the metal element 14undergoes bending deformation so as to close the space α by means of thepushing force acting between the metal elements 14, and there istherefore a possibility that degradation of the strength and degradationof the power transmission efficiency will occur.

On the other hand, FIG. 4 (A) corresponds to the metal element 14 of thepresent embodiment, which has the first recess 20. In the ComparativeExample, the starting point of the triangular space α coincides with thecenter of rotation O of the middle in the left-and-right direction ofthe metal element 14, but in the present embodiment since the firstrecess 20 is formed in the front face of the metal element 14 on the farside, the starting point of a triangular space α is at a point O′, whichis displaced toward the right end of the first recess 20. As a result,in the Comparative Example the distance from the point O, which is thestarting point of the space α, to the end point of the space α is L1,whereas in the present embodiment the distance from the point O′, whichis the starting point of the space α, to the end point of the space α isL2 (>L1).

Therefore, when the metal element 14 undergoes bending deformation so asto close the space α by means of the pushing force acting between themetal elements 14, since in the Comparative Example it is necessary toabsorb the bending corresponding to the gap g in a range of distance L1,whereas in the embodiment it is only necessary to absorb the bendingcorresponding to the gap g of the same degree in a range L2, which islonger than L1, it is possible to reduce the bending stress (or amountof relative deformation) of the body part 15 connected to the neck part16 of the metal element 14, thus minimizing degradation of the strengthand degradation of the power transmission efficiency.

Second Embodiment

A second embodiment of the present invention is now explained byreference to FIG. 5 to FIG. 7.

In the first embodiment, the first recess 20 is formed on the front faceside of the metal element 14, but as shown in FIG. 5 in the secondembodiment, in addition to a first recess 20, a second recess 20′ isfurther formed on the rear face side of a metal element 14. The width inthe left-and-right direction of the second recess 20′ is the same as thewidth in the left-and-right direction of the first recess 20, but sinceno inclined face 15 b is formed on a rear face of a body part 15 of themetal element 14, the radially inner end of the second recess 20′reaches the radially inner end of the body part 15.

As explained for the first embodiment, due to the first recess 20 beingformed on the front face side of the metal element 14, even when themetal element 14 on the front side and the metal element 14 on the rearside move relative to each other in the radial direction or in therotational direction, it is possible to minimize the bending stress onthe metal element 14, thereby minimizing degradation of the strength anddegradation of the power transmission efficiency. As shown in FIG. 6 andFIG. 7, since the second recess 20′ formed on the rear face side of themetal element 14 also exhibits the same function as the first recess 20described above, the second embodiment, which has both the first recess20 and the second recess 20′, can achieve the same operational effectsas in the first embodiment.

Third Embodiment

A third embodiment of the present invention is now explained byreference to FIG. 8 and FIG. 9.

As shown in FIG. 8, a metal element 14 of the third embodiment includesa first recess 20 in a front face and a third recess 20″ in a rear face.The first recess 20 is formed so as to extend from one part on theradially inner end side of a neck part 16 to a body part 15.Furthermore, the third recess 20″is formed so as to extend from one parton the radially outer end side of the neck part 16 to an ear part 17.The width in the left-and-right direction of the first recess 20 and thewidth in the left-and-right direction of the third recess 20″ areidentical and constant in the radial direction. The radially outer endof the first recess 20 is further radially inward than the radiallyinner end of the third recess 20″, and the first recess 20 and the thirdrecess 20″ do not overlap one another when viewed in the fore-and-aftdirection.

Therefore, a flat portion 16 a that is one step higher than the firstrecess 20 is formed on a front face of the neck part 16, and a flatportion 16 b that is one step higher than the third recess 20″ is formedon a rear face of the neck part 16, the flat portions 16 a and 16 boverlapping one another when viewed in the fore-and-aft direction. Theflat portion 16 a on the front face of the neck part 16 is flush withflat portions 17 c and 17 c of the ear part 17 and a rocking edge 19,and the flat portion 16 b on the rear face of the neck part 16 is flushwith a part other than the third recess 20″.

In accordance with the present embodiment, not only can the same effectsas in the first embodiment be achieved by the first recess 20, but thefollowing further effects can also be achieved. That is, as shown inFIGS. 9 (A) to (F), due to the flat portions 17 c and 17 c of the earpart 17 of the metal element 14 on the rear side abutting against a rearface of the ear part 17 of the metal element 14 on the front side andthe flat portion 16 a of neck part 16 of the metal element 14 on therear side abutting against the flat portion 16 b of the neck part 16 ofthe metal element 14 on the front side, it is possible to stabilize theattitude of the metal element 14, thereby minimizing degradation of thepower transmission efficiency.

In addition, as shown in FIGS. 9 (E) and (F), when the metal element 14on the rear side is displaced toward the radially outer side withrespect to the metal element 14 on the front side and moves forward sothat the rocking edge 19 of the metal element 14 on the rear side entersthe ring slots 18 and 18 of the metal element 14 on the front side,since the flat portion 16 a of the neck part 16 of the metal element 14on the rear side cannot move forward due to interference with the flatportion 16 a of the neck part 16 of the metal element 14 on the frontside, the radially outer end of the metal element 14 attempts to fallrearward. However, since the metal element 14 on the rear side undergoeselastic deformation due to a pressing force from a metal element 14further to the rear side, adjacent metal elements 14 and 14 can maintaina mutually parallel positional relationship.

Embodiments of the present invention are explained above, but thepresent invention may be modified in a variety of ways as long as themodifications do not depart from the spirit and scope thereof.

For example, in the embodiments the radially inner edge 20 a of thefirst recess 20 reaches the inclined face 15 b of the body part 15, butthis is not always necessary, and a radially inner edge 20 a of a firstrecess 20 may extend from a neck part 16 to part of a body part 15 whilebridging a rocking edge 19.

Furthermore, in the embodiment the radially inner end of the secondrecess 20′ reaches the radially inner end of the body part 15, but thisis not always necessary, and the radially inner end of a second recess20′ may extend from a neck part 16 to part of a body part 15 whilebridging a rocking edge 19.

1-3. (canceled)
 4. A metal belt for a continuously variabletransmission, the metal belt, which is wound around a drive pulley and adriven pulley and transmits a driving force between the two pulleys,comprising a pair of metal ring assemblies that are arranged side byside in a left-and-right direction and a large number of metal elementsthat are latched to the pair of metal ring assemblies in a state inwhich the metal elements are stacked in a fore-and-aft direction, themetal element comprising a pair of ring slots with which the pair ofmetal ring assemblies engage, a neck part that is positioned between thepair of ring slots, a body part on which is formed a saddle face that iscontinuous with a radially inner side of the neck part and supports aninner peripheral face of the pair of metal ring assemblies, and an earpart that is continuous with a radially outer side of the neck part andopposes an outer peripheral face of the pair of metal ring assemblies,and a rocking edge being provided at a radially outer end of a frontface of the body part, the rocking edge being a fulcrum for pitching ofthe metal element, wherein a first recess extending from the ear part tothe body part is formed in front faces of the ear part and the bodypart.
 5. The metal belt for a continuously variable transmissionaccording to claim 4, wherein a second recess extending from the neckpart to the body part is formed in rear faces of the neck part and thebody part.
 6. A metal belt for a continuously variable transmission, themetal belt, which is wound around a drive pulley and a driven pulley andtransmits a driving force between the two pulleys, comprising a pair ofmetal ring assemblies that are arranged side by side in a left-and-rightdirection and a large number of metal elements that are latched to thepair of metal ring assemblies in a state in which the metal elements arestacked in a fore-and-aft direction, the metal element comprising a pairof ring slots with which the pair of metal ring assemblies engage, aneck part that is positioned between the pair of ring slots, a body parton which is formed a saddle face that is continuous with a radiallyinner side of the neck part and supports an inner peripheral face of thepair of metal ring assemblies, and an ear part that is continuous with aradially outer side of the neck part and opposes an outer peripheralface of the pair of metal ring assemblies, and a rocking edge beingprovided at a radially outer end of a front face of the body part, therocking edge being a fulcrum for pitching of the metal element, whereina first recess extending from the neck part to the body part is formedin front faces of the neck part and the body part, and the first recessis formed so as to extend from one part of the neck part to the bodypart, a third recess extending from one part of the neck part to the earpart is formed in rear faces of the neck part and the body part, and thefirst recess and the third recess are positioned so as not to overlapone another when viewed in the fore-and-aft direction.